Petroleum Coke is produced in oil refineries as a by-product of the cracking of crude oil into a wide range of products. The crude is heated at high temperature and pressure in the presence of a catalyst to break down the heavy hydrocarbon molecules into lighter fractions; petroleum coke is essentially the solid residue of carbon left after all the liquid and gaseous products have been extracted. It represents less than 10% by weight of the original crude supplied to the refinery. The production of the lighter fractions (petroleum spirit, heating oil etc.) provides the economic justification for the process plant required; petroleum coke is a by-product of the process, but despite being a by-product it has a commercial value in various applications. Petroleum coke can be classified into various groupings: Anode grade coke is relatively pure and is used in dry cell batteries where it forms the anode; Fuel grade coke is used in power generation. It has a high calorific value and low ash content, but its high sulfur content raises environmental problems in the form of SOx emissions requiring flue gas treatment. At the same time, its low content of volatile compounds (all removed in the refinery) make it difficult to burn, and advanced FBC boilers are necessary; Calcined petroleum coke is produced by treating the green coke from the cracking process to drive off any remaining volatile compounds. This grade is mainly used for the electrodes in metallurgical arc furnaces, for example in aluminum production. However, this application requires low metal contents in the final anodes to avoid introducing impurities into the aluminum. The metal content of the petroleum coke depends on the quality of the crude oil feeding the refinery, and crudes may have to be blended to achieve the correct quality in the final coke (a more effective approach than trying to blend the final product). The major producer of petroleum coke in 2006 (UN figures) was the USA at 57,147,000 metric tons. This was well ahead of the next largest producer, China with production of 9,899,000 metric tons. Many other countries are also producers, but in much smaller quantities. The average June 2009 US price of petroleum coke for power generation was US$1.53/mmbtu. References: